This invention relates to a power distribution circuit for quartering and distributing a single input.
FIG. 1 is a front view of a prior-art power distribution circuit. In the figure, numeral 1 designates a dielectric substrate, numerals 2-7 designate distributed constant lines, numerals 8-10 designate resistances, numerals 11 and 12 designate connecting lines, numerals 13-15 desginate Wilkinson type bi-distribution circuits, numeral 16 designate an input terminal, and numerals 17-20 designate output terminals.
The Wilkinson type bi-distribution circuit 13 is composed of the distributed constant lines 2 and 3 and the resistance 8, the Wilkinson type bi-distribution circuit 14 is composed of the distributed constant lines 4 and 5 and the resistance 9, and the Wilkinson type bi-distribution circuit 15 is composed of the distributed constant lines 6 and 7 and the resistance 10.
The Wilkinson type bi-distribution circuits 13 and 14 are connected by the connecting line 11, while those circuits 13 and 15 are connected by the connecting line 12.
The distributed constant lines 2-7 and the connecting lines 11, 12 are formed of a microstrip on the dielectric substrate 1, and the resistances 8-10 are also formed on the dielectric substrate 1 by vapor deposition.
Letting Z.sub.O denote the characteristic impedance of a power supply, the characteristic impedance of each of the distributed constant lines 2-7 is selected at .sqroot.2 Z.sub.O, and the value of each of the resistances 8-10 is selected at 2 Z.sub.O. The electrical distance of each of the distributed constant lines 2-7 is selected at a quarter wavelength.
By selecting the characteristic impedance and electrical distance of each of the distributed constant lines 2-7 and the magnitude of each of the resistances 8-10 at such values, a microwave signal having entered the input terminal 16 is quartered and then distributed to the respective output terminals 17-20. Moreover, isolation is held between the respectively adjacent ones of the output terminals 17-20. This is effective for the power distribution circuit because, due to connections between amplifiers and the respective output terminals 17-20 of the power distribution circuit by way of example, when only the amplifier connected to the output terminal 17 has broken down due to any cause, the breakdown does not affect the amplifiers connected to the other output terminals 18-20.
The power distribution circuit of this type, however, has had the disadvantage that three Wilkinson type bi-distribution circuits are required, resulting in large geometries.